Fuel injection unit



Dec.' 30,1369 'ADREISM 3,486,493

FUEL INJECTION UNIT Filed Feb.'l3, 1968 3 Sheets-Sheet l Dec. 30, 1969A. mzlsm 3,486,493

7 FUEL INJECTION UNIT 7 Filed Feb. 15, 1968 3 Sheets-Sheet 2 SZI UnitedStates Patent 3,486,493 FUEL INJECTION UNIT Alexander Dreisin, OlympiaFields, 111., assignor to Allis-Chalmers Manufacturing Company,Milwaukee, Wis.

Filed Feb. 13, 1968, Ser. No. 705,176 Int. Cl. F02m 39/00; F02d 1/04,N06 US. Cl. 123139 10 Claims ABSTRACT OF THE DISCLOSURE A fuel injectorand a hydraulic pressure control unit for controlling initiation andtermination of fuel injection.

p This invention relates to a fuel injector and more particularly to ahydraulic control unit for controlling the timing and fuel delivery rateof the fuel injector.

A fuel injector is a well-known device used to supply fuel in a highlyatomized state to the combustion chamber of the internal combustionengine. The injector is usually actuated mechanically by means of a camwhich is driven by an engine usually through a gear train. The cammotion is transmitted through a mechanical linkage to a reciprocatingplunger which during the pumping stroke displaces fuel which is fed tothe nozzle which injects the fuel through spray orifices into thecombustion chamber.

The conventional unit injector is mechanically actuated, andmechanically controlled by a control device which senses engine speedand throttle position and is connected to each unit injector bymechanical linkages. Movement of the linkages is transmitted to the unitinjector plunger which varies the effective length of the stroke. Themechanical connection between the control device such as a governor andthe individual injectors increases in complexity with the increasingnumber of engine cylinders. It induces friction into the control systemwhich requires higher control forces from the governor and requiresmaintenance because a change in the relative position of thesemechanical linkages can disurb the output balance of the individualinjectors. In addition the injector timing is fixed in relation to theengine cycle.

A modification of the unit injector provides that the fuel quantity ofeach injection is premetered separately at low pressure by anotherdevice and is preloaded into the injector pumping chamber preceding eachstroke. This system does not require mechanical control linkages but hasa disadvantage of injecting the fuel froin an intermediate portion ofthe plunger stroke to the bottom of the plunger stroke or the top of thecam lift. Such injection has inherent disadvantages, namely, the endportion of the injection occurs at decreasing plunger velocity whichadversely affects the atomization of the fuel and subsequently thequality of combustion. Another disadvantage common with the firstdescribed type of unit injector is that the system also has fixedinjection timing Modern engine speeds of diesel engines are increasingand it becomes necessary to change the relative timing between fuelinjection and the engine combustion cycle. At low engine speed theoptimum position of injection start can be close to the engine top deadcenter at the end of the compression stroke. As the engine speedincreases,

Patented Dec. 30, 1969 the engine crankshaft turns through a largerangle during the time required to prepare the injected fuel forcombustion. This preparation time consists essentially in the timerequired to preheat and partially evaporate the injected droplets offuel and the time needed to accomplish the so-called prefiame oxidationreactions. As an example this might be on the order of two crankshaftdegrees at 600 engine r.-p.m. and twelve crankshaft degrees at 3000engine r.p.m. For optimum conditions throughout the speed range,injection timing therefore should be advanced by about ten crankshaftdegrees in respect to the engine top dead center.

The proposed hydraulically controlled unit for initiatin g andterminating injection eliminates the disadvantages of the conventionalinjector systems without adding to the overall system complexity. Thecontrol unit is designed to supply to the individual injectors the fuelwhich was originally pressurized by a supply pump and to distribute tothe individual injectors control pulses or hydraulic pressure signals toinitiate and terminate injection. The control unit governs the timingand the durations of the pressure signals as a function of engine speedand throttle position.

The control pulses or pressure signals change the pressure supplied tothe control valve in the injector during movement of the pump plunger.The differential pressure created by the pressure signals cause thecontrol valve to close which interrupts communication between thepumping chamber and the drain passage and initiates fuel injection.

Reestablishment of the supply pressure to the control valve eliminatesdifferential pressures acting on the control valve which cause thecontrol valve to open the communication between the pumping chamber andthe drain passage and thereby terminate fuel injection. Supply andambient pressures are referred to in the description of this inventionto illustrate the operation of the injection. It is understood that onlya change in pressure is required to control injection and the specificpressures or magnitude of the change is not critical.

It is an object of this invention to provide a fuel injector havingcontrol means for supplying two levels of supply presure to initiate-andterminate injection.

It is another object of this invention to provide a fuel injectorcontrol by a change in fuel supply pressure to initiate fuel injectionand reestablishing initial fuel supply pressure to terminate fuelinjection.

It is a further objection of this invention to provide a control unitsensitive to speed and/or a manual control control such as the throttleso as to change the timing and duration of fuel injection.

It is a further object of this invention to provide a control for timingand duration of fuel injection by changing and reestablishing supplypressure to the fuel injector.

It is a further object of this invention to provide a combination fueldistributor and pressure control for initiating and terminatinginjection and angularly dephasing a control element to regulateinjection timing and axially displacing the control element to meter thequantity of fuel injection.

The objects of this invention are accomplished through the use ofmechanically actuated fuel injection pumps for injection of highpressure fuel sequentially into a plurality of combustion chambers. Acontrol valve controls the initiation and termination of fuel injectionand is positioned in the hydraulic line supplying and returning fuel forcooling of the injector and the nozzle during the phase of the cyclewhen the injector is not in the process of injection. The control valvehas a chamber which receives fuel from the control unit which enters atthe supply line pressure. The return passage from the fuel injector isalso in communication with the control valve and fuel normally passesthrough a return line to the fuel supply. The control unit includes arotating shaft rotating synchronously with the engine and also has adistributor housing and distributor stator with a plurality of deliverypassages in communication with unit injectors. Radially intermediate theshaft and the stator is positioned a distributor rotor which is adaptedfor movement axially to control injection quantity and angularly tocontrol injection timing relative to the shaft. The movement of thedistributor rotor relative to the shaft is controlled by a governordriven sleeve. Dephasing the rotor angularly in reference to thedistributor stator changes injection timing without affecting injectionduration. Axial displacement of the rotor in reference to thedistributor stator varies injection duration, which in turn governs theinjected quantity.

The preferred embodiment of this invention will be described in thefollowing paragraphs and illustrated in the attached drawings.

FIG. 1 schematically illustrates a hydraulic system for fuel injection.

FIG. 2 illustrates a cross section of the injector.

FIG. 3 illustrates a cross section view taken on line III-III of FIG. 1.

FIG. 4 illustrates a cross section view of the control unit.

FIG. 5 is a cross section view taken from line V--V of FIG. 4.

FIG. 6 is a cross section view taken on line VIVI of FIG. 4.

FIG. 7 is a three dimensional view of the distributor rotor in solidlines and the distributor stator in phantom lines with its slots indotted lines.

FIG. 8 is a developed view of the distribution stator in solid lines andthe distributor rotor in dotted lines at 30 before engine top deadcenter with rotor advanced and the throttle in wide open position atstart of injection.

FIG. 9 is a view showing stator and rotor positions at the end ofinjection with throttle in wide open position.

FIG. 10 is a view similar to FIG. 8 at the start of injection withthrottle in no fuel position. The view includes directions of shaftrotation, timing, and throttle movement which are common to FIGS. 8, 9,and 10.

FIG. 11 is a view similar to FIG. 8, 30 degrees before top dead centerwith the rotor in the retarded position and throttle in wide openposition.

Referring to the drawings, FIG. 1 illustrates a schematic drawing of thehydraulic system. The fuel tank 1 is connected to the low pressureconduit 2 through fuel filters to the supply pump 3. The supply pump 3develops a steady flow of fuel at a constant pressure of 50 to 100pounds per square inch approximately. The fuel is supplied to thecontrol unit 4 which is driven by the engine at a constant speed ratiowith the engine. The control unit 4 has a fuel return line 5 undersubstantially ambient pressure which returns excess fuel back to thetank 1. In addition the control unit is connected by individual supplylines 6 to the respective injectors 7. These lines 6 are subjectedalternately to the supply pressure or to the ambient pressure as will befurther described. The two pressures applied to the injectors are notcritical, but it is the changing of the pressure levels that controlsinjection.

After passing through the injectors the fuel passes through the drainlines 8 and the manifold 9' through 4 the relief valve 10 and back tothe tank by the return line 11.

Each of the unit injectors 7 are cam actuated by the engine and the camimparts reciprocating motion to the plunger 12 which is closely fittedinto the bore of the housing 13. During the interval between injectionsfuel under supply pressure is furnished by the line 6 which fills thecontrol spring chamber 14. From there it passes through a drilledpassage 15 in the housing and through the inlet portion 16 into theinjection pumping chamber 17. The fuel then flows through the passage 18int-o the gallary 19 surrounding the valve 20 and continues its flowthrough the passages 21 and 22 to the control annulus 23 which surroundsthe control valve 24. The control valve is formed with radial slots 25through which the fuel flows from the annulus 23 and through theclearance between the control valve and the stem of the adjusting screw26. It then passes unobstructed through the passage 27 to the drain line8 into the drain manifold 9. The circuit is completed across thepressure relief valve 10 which is set at approximately 50 to 100 poundsper square inch and through the valve drain line 11 back to the fueltank.

From the above flow path description it is clear that the pressure inthe drain lines 8 and the manifold 9' is of the same order as in thesupply lines '6. A small difference will only be induced by theresistance to flow of the passages inside of the unit injectors whichare arranged in parallel. In the first approximation and for simplicityof further explanation we can assume the pressure in the lines 8 and themanifold 9 is equal to the supply pressure furnished by the pump 3 tothe control unit 4.

The control unit is designed to supply to the unit injectors the fuelwhich was originally pressurized by the supply pump, and to distributeto the individual injectors controlled pressure pulses. The control unitgoverns the timing and duration of the pressure changes as a function ofengine speed and throttle position.

Referring to FIG. 4 the control unit is mounted on the engine and drivensynchronously at half engine speed for four stroke cycle engine and atengine speed for two stroke cycle engines. This driven is transmitted bythe drive shaft 40 to the governor weights 41 by the governor carrier 42which is pinned to the shaft. The axial prongs 43 of the shifter sleeve44 fit slideably between the arms of the governor carrier 42 and allowthe sleeve to move axially in relation to the drive shaft 40. Theshifter sleeve is equipped at its opposite end with one or more timingslots 45 which engage the pins 46 which are pressed into the distributorrotor 47. The distributor rotor 47 is closely fitted to the distributorstator 48 in which it can move rotatably and can slide axially. A timingspring 49 is arranged around the drive shaft 40 between the shiftersleeve 44 and the snap ring 50 positioned inside the rotor 47.

Governor spring lever 51 transmits the force of the governor spring 52to the rotor across the flanged end 53. The opposite end of the governorspring abuts against the governor throttle lever 54. Varying theposition of this lever preloads the governor spring to higher or lowerforces.

Fuel lines 6 connect the individual injectors with the distributorstator through the radial passages 55 arranged in the central portion ofthe distributor stator and through the slots 56. The arrangement of thecontrolling parts on the rotor and stator is shown for greater clarityin FIG. 7.

As shown in FIG. 4 the supply annulus 57 is in constant communicationwith the supply pump through passage 58 located in the control unithousing 101 and the distributor stator 48 which is also in communicationwith the annular recess 59 in the rotor shown in FIG. 4. A spill slot 61is also shown in FIG. 4 and FIG. 5. The distributor stator is formedwith the plurality of distributor slots 56, and the pressure reliefslots 60 which are maintained at substantially ambient pressure throughthe annular chamber 100 which is in communication with the ambientpressure inside of governor housing.

The distributor rotor 47 moves axially and angularly relative to theshaft 40. The distributor rotor 47 forms the annular recess 59 with oneside of the recess defining an axially extending tooth 102 having aleading and a trailing edge. Referring to FIG. 7 the tooth 102 ofdistributor rotor 47 operates as a pressure interrupter while the spillslot 61 sequentially relieves the pressure in the distributor slots 56through relief slots 60.

Referring to FIGS. 7, 8, 9, 10 and 11 the distributor stator is shownwith a plurality of distributor slots 56 each of which is incommunication with a unit injector. Similarly a plurality of pressurerelief slots 60 are shown which relieve the pressure in the distributorslot 56 sequentially to govern the timing of the injection.

FIG. 8 illustrates the annular recess 57 which supplies the annulus 59in the distributor stator 47. The pressure interruption and relief willbe described in the subsequent paragraphs in the operation.

The operation of the injector and the hydraulic system will be describedas well as the control unit which interrupts and relieves the pressureand subsequently restores pressure on the control valve in each injectorto initiate and terminate injection. As shown the tooth 102 has an axialleading edge and a diagonal trailing edge. The angular displacement ofthe rotor relative to the shaft 40 controls timing of fuel injectionwhile the axial displacement of the distributor rotor controls quantityof fuel delivery.

At the beginning of the cam stroke the plunger 12 starts its pumpingmotion. At this time the fuel is flowing through the pumping chamber tothe nozzle and cools the nozzle in its passage and is returned to thetank 1. During its pumping movement the edge 28 of the plunger 12 willoverride the intake port 16 and will close it. Past this point theadvancing plunger still displaces the fuel in the injector which flows,as previously described, through the control valve 24 to the drainmanifold. At the appropriate time in relationship to the engine cyclethe control unit 4 relieves the pressure in the supply line 6 leading tothe particular injector 7.

Considering the control valve 24 prior to the start of injection it wassubject to essentially the same pressure on its upper and lower faces.Its lower face on the side of the spring control chamber 14 was subjectto the supply pressure arriving through the line 6. Its upper face onthe side of the adjusting screw 26 was subject to the same pressurediminished onlyby the resistance to the fuel flow through the passages18 through 22 of the unit injector. Control spring 29 exerts aforcewhich is approxr imately equal to one-half the axial force exerted on'the valve 24 by the supply pressure. As long as the supply pressure inchamber 14 exists the sum of the forces of the spring and the hydraulicpressure force on the control valve in the direction of the adjustingscrew 26 maintains the valve open. The valve is stopped by the pin 30which is located across the stern of the adjusting screw 26 and extendsthrough opening in the control skirt. When hydraulic pressure is loweredin the spring chamber 14 the force of the spring 29 is overcome by thehydraulic force which is acting on the valve from the side of theadjusting screw 26.

The control valve moves against the spring. Slots 25 override the edgeof the annulus 23. This stops the flow of fuel from the nozzle passage22. The continuing movement of the plunger 12 now compresses the fueltrapped in the chamber 17 and the nozzle passages 18 through 22. Whenthe opening pressure of the needle is exceeded the nozzle opens in aconventional manner and the injection takes place. To terminate theinjection, pressure has to be reestablished in the chamber 14. At thatmoment the hydraulic force in the spring chamber will balance thehydraulic force on the opposite side of the valve and the spring willshuttle the valve to an open position. Reopening of the valve slots willreestablish communication to the return manifold 9 which will drop thepressure in the unit injector below the closing pressure of the nozzle.This will cause the nozzle to close and will terminate the injection.

The described unit injector can be controlled by dropping the supplypressure to ambient which initiates injection and reestablishing thesupply pressure which terminates the injection. Varying the phasing ofthis event in relation to the engine will vary the injection timing.Varying the time interval between relief of supply pressure and thereestablishing of supply pressure will change the portion of the plungerstroke during which time the fuel is trapped in the injector and,therefore, will change the fuel quantity injected through the nozzle.The duration of the interval of low pressure therefore determines theeffective plunger stroke of the injector.

The valve 24 is provided with an adjusting screw 26 which adjusts themovement of the skirt required to close the annulus 23. A springadjusting screw 31 controls the spring tension and the rate at which thevalve will respond to changing pressures on opposing sides of the valveelement. The valve may be adjusted to the pressure signals of supplypressure relief and reestablishment of supply pressure on the valve toproduce a repeatable time interval controlling injection.

The control unit functions in the following manner. Filtered fuel issupplied by the supply pump at approximately 50 to pounds per squareinch and is continually being fed to the supply annulus 57 in thedistributor stator 48. It also fills the annular recess 59 in the rotor,the distributor slots 56, radial passages 55, and supply lines 6 andflows continually through the injectors as previously described.

Let us consider what happens to an injector connected with thedistributor slot 56a as shown in FIG. 8. Assume that at this point theengine is approximately 30 degrees before top dead center on acompression stroke. Further let us assume that the throttle lever 54 hascompressed the spring 52 to a force corresponding to a wide openposition on the engine. Governor spring lever 51 has been pushed againstthe stop 62 and has forced the rotor all the way to the left as shown inFIG. 4. Axial portion of the metering edge 63 of tooth 102 has justpassed the trailing edge of distributor slot 56a shutting offcommunication between fuel under supply pressure in the annular recess59 and the unit injector communicating with the distributor slot 56a. Asshown in FIG. 8 the spill slot 61 has established communication betweenthe distributor slot 56a and the corresponding pressure relief slot 6011on the right-hand end of the stator. The pressure relief slots are incommunication with the interior of the governor housing 101, which inturn has a relief line 5 as shown in FIG. 1 to the tank. The pressurerelief slots are therefore at a substantially ambient pressurethroughout the control cycle. The moment communication is establishedbetween a distributor slot and a pressure relief slot across the spillslot the supply pressure in that particular fuel line and unit injectoris dropped to ambient pressure initiating injection as described above.Distributor and pressure relief slots are dephased angularly in therotor in such 'a way that communication between them can be establishedand terminated over very short angles of rotation, for example threedegrees after the spill slot overrides the leading edge of a distributorslot, its training edge can be made to override the trailing edge of apressure relief slot. This is important because for small injectionquantities we have to be able to reestablish supply pressure in the fuelline shortly after the pressure drop in order to terminate theinjection. For no load operation injection duration required might be onthe order of l to 3 degrees of engine rotation. The angular phasing ofthe distributor and pressure slots is chosen to satisfy this conditionand is fixed during manufacturing. Examining FIG. 8 it is evident thatall the rest of the distributor slots and injectors are still incommunication with the annular recess 59 and are therefore receiving asteady flow of fuel under supply pressure.

FIG. 9 shows the end of injection in wide open throttle position. Herespill slot 61 has passed the trailing edge of slot 56a interruptingcommunication to the low pressure side. The inclined portion of themetering edge of tooth 102 has come into contact with the leading cornerof the distributor slot 56a. In its further movement this inclined edgewill begin to override the corner of this slot, reestablishingcommunication between the slot 56:: and supply pressure in the annularrecess 59. Fuel can now flow under supply pressure through slot 56a,passage 55 and line 6 to the injector and, upon arrival, will open valve24. This will terminate injection.

Referring to FIG. 10 the start of injection is shown in no fuelposition. In this position the rotor 47 has moved axially to the rightor shut off position, As is evident from this view, the inclined portionof the metering edge reestablished communication between injector andsupply pressure immediately after pressure was dropped through theregistry of the spill slot with distributor and the pressure reliefslots.

In actual operation this can take place for example at high speed idle.When engine load has been reduced externally while the throttle is inwide open position, engine speed will increase which in turn willincrease the centrifugal force developed by the governor weights 41.This force is transmitted through the governor fingers 64, shiftersleeve prongs 43, timing spring 49, and snap ring 50 to the' rotor 47.This force will overcome the governor spring force and move the rotor tothe right towards the no fuel position and decrease the fuel quantity.

The fuel quantity can also be decreased by moving the manual throttlelever 54 from the wide open position to a part load position shown indotted lines in FIG. 4. This will decrease the governor spring force.The centrifugal force which had previously balanced the spring forceWill now overpower the governor spring and will move the rotor to theright to a reduced fuel quantity.

The above description should clarify the metering function of thecontrol unit. The timing function is explained in the following bycomparing FIG. 8 with FIG. 11. In both cases the rotor is shown in wideopen position. FIG. 8 shows the start of injection at 30 degrees beforetop dead center at rated engine speed. At this speed the governorweights are in half open positions as shown in FIG. 4 and are balancingthe governor spring force. Assume that the engine speed is beginnnig todecrease due to an external overload and as the engine speed begins tofall off the centrifugal force decreases. Axial rotor position remainsthe same because it is dictated by the position of spring lever 51 whichis forced against the stop 62 by the force of the governor spring 52;but the decreasing axial force acting on the shifter sleeve will forcethe timing spring 49 to expand moving the shifter sleeve left towardsthe weight assembly. The changing relative position between the shiftersleeve and the rotor will cause an angular relative movement between theinclined timing slot 45 and the pin 46 retarding the rotor in relationto the driving shaft and because of it in relation to the engine cycle.FIG. 11 shows a relative position between the stator 48 and the rotor 47at the same moment of the engine cycle, 30 degrees before top deadcenter, but at low engine speed. While at the high engine speed shown inFIG. 8, this was the start of injection, at low engine speed the spillslot has not yet reached the leading edge on the distributor slot 56aand injection is retarded.

The number of distributor slots and pressure relief slots corresponds tothe number of engine cylinders. When applied to a four stroke cycleengine the control unit drive shaft 10 is driven at one-half enginespeed.

For two stroke cycle engines the control unit would be driven at enginespeed the rest of the construction remaining the same.

The preferred embodiments of this invention have been illustrated anddescribed and the attached claims will define the scope of thisinvention.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A fuel injector control unit for producing fluid pressure signals foruse with a fuel injector operated by a pressure control valve toinitiate and terminate fuel injection in response to fluid pressuresignals comprising, a control unit including, a rotary member an enginedriving said rotary member and rotating at a variable speed bearing aninteger ratio with the speed of rotation of said rotary member, a speedand a manual responsive means sensing the speed and controlling the loadof said engine, a distributor rotor defining an annular recess partiallyfilled by an axial tooth pressure interrupter and rotating withsaid-rotary member and connected to said speed and manual responsivemeans for shifting relative to said rotary member in response to themanual responsive means and the speed of said engine, a distributorstator defining distributor slots and pressure relief slots angularlyspaced about its" periphery with said distributor slots in fluidcommunication with said annular recess of said distributor rotor andconnected to at least one fuel injector for supplying fuel to saidinjector, fuel supply means defining supply passage means for supplyingpressurized fuel to said annular recess in said rotor of said controlunit, said pressure interrupter of said distributor rotor defining aspill slot sequentially connected distributor slots and relief slots forchanging and restoring pressure of the fuel supply to said injector tothereby control the timing and duration of the pressure signals relativeto engine rotation.

2. A fuel injection control unit as set forth in claim 1 wherein saidrotary member is connected to said speed responsive means comprising agovernor to advance and retard timing of pressure signals relative toengine rotation.

3. A fuel injection control unit as set forth in claim I wherein saiddistributor rotor is connected to said speed and manual responsive meanscomprising a governor and a throttle respectively to control theduration of pressure signals.

4. A fuel injection control unit as set forth in claim 1 wherein saiddistributor stator receives pressurized fuel from the fuel supply and aplurality of fuel injectors are connected to the control unit.

5. A fuel injection control unit as set forth in claim 1 wherein thepressure interrupter of said distributor rotor defines a barrier tofluid flow and said spill slot relieves pressure'applied to saidinjector for sequentially changing pressure applied to the control valvesaid fuel injector.

6. A fuel injection control unit as set forth in claim 1 wherein saiddistributor stator defines a plurality of distributor slots each incommunication with a mating injector and a plurality of pressure reliefslots located in sequence to relieve pressure in each of saiddistributor slots, the tooth interrupter of said distributor rotorinterrupts pressure supplied to each of the plurality of fuelinjectorsand said spill slot provides communication between thedistributor slot and pressure relief slots to relieve pressure forapplying to said injector to initiate fuel injection in each of the fuelinjectors.

7. A fuel injector control unit as set forth in claim 1 wherein thetooth pressure interrupter interrupts pressure upon covering adistributor slot and said spill slot relieves pressure upon connectingsaid distributor slot with said relief slot, said interrupter restoresthe original pressure by uncovering said distributor slot to provide twolevel pressure signals adapted for initiating and terminating fuelinjection of said injector.

8. A fuel injector control unit as set forth in claim 7 wherein saidtooth pressure interrupter defines an axial leading edge and an axialspill slot to control relieving pressure to said fuel injector.

9. A fuel injector control unit as set forth in claim 1 9 10 wherein thetiming control includes a governor advancing References Cited andretarding said rotor angularly relative to said rotory UNITED STATESPATENTS member, a throttle lever controls the axial position of said 1919 601 7/1933 Simmen rotor relative to said stator to thereby controltiming and 2:916:028 12/1959 Mansfield duration of pressure signalsadapted for controlling the 5 3,375,811 4/1968 Morris 123 139 m g n q ny f f l inj n. 3,416,506 12/1968 Steiger 123 139 10. A fuel injectorcontrol unit as set forth in claim 1 wherein said tooth pressureinterrupter defines a diagonal trailing edge controlling the restorationof pressure 10 US, Cl, X R applied to said injector. 123140 LAURENCE M.GOODRIDGE, Primary Examiner UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION Patent: No. 3A A93 Dated December 30, 1969 Inventor-(s)Alexander Dreisin It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Column 8, line 28, "connected" should read connecting line 38, "I"should read 1 and line 7 4, after the word "pressure" insert appliedSIGNED AN'D SEALED MAY 12197 (SEAL) Attest:

Edward M. Fletcher, Jr.

Auesting Officer WILLIAM SOHUYLER mmissione-r of Patents

